Method and means for securing modified localized areas in pulp molded articles



2,961,368 FOR SECURING MODIFIED LOCALIZED s E L C T. m. An SD N E om YO LM Rw .U HP N MT.. S rR DA N A D m 0m 6M 9 1 2, 2 v. o N

2 Sheets-Sheet 1 Filed June 6, 1957 QfdM/fomdf Kw... @was Nov. 22, 1960 H R, LYONS 2,961,368

METHOD AND MEANS FOR SECURING MODIFIED LOCALIZED AREAS IN PULP MOLDED ARTICLES 2 Sheets-Sheet 2 Filed June 6, 1957 YUnited, States Patent @fire 2,961,368 Parental Nov. 22,1960

Herbert R. Lyons, New Canaan, Conn., assignor to Diamond National Corporation, a corporation of Dela- Ware Filed June 6, 1957, Ser. N0.664,120

Claims. (Cl. 162--219) This invention relates to apparatus and methods for producing locally modified molded articles and locally modified or reinforced molded pulp articles.

In the manufacture of molded articles which may be of molded pulp, it is sometimes desirable to provide localized'reinforcement in selected areas of the articles to change the normal structure thereof or to improve the strength or wear resistance thereof. For example, in a conventional molded pulp egg carton having an integral hinge for its cover, it is desirable to reinforce the hinge portion of the egg carton in order to provide increased bending strength therein. In the past, localized reinforcement of molded pulp articles has been attempted by depositing an extra thickness of pulp fibers in limited areas during the molding operation. Sometimes selected portions of the completely molded article havewbeen coated or impregnated with certain plastic compositions toV provide such reinforcement. It has also been suggested that reinforcement could be achieved Vif a satisfactory method or apparatus could be devised for depositing a superior grade of pulp stock in a given limited area. Thus, in forming an article molded principally from ground wood pulp stock, some longber pulp stock could be deposited in the areas where-reinforcement is desired. However, no entirely satisfactory methods and apparatus for performing this operation on a continuous high speed production basis have been devised or available heretofore.

An object of the present invention is Vto provide new and improved methods of and apparatus for producing locally modified molded articles. n

Another object of the invention is to provide new and improved methods of and apparatus for producing locally reinforced molded pulp articles on a continuous high speed production basis. n

Still another object of 'the invention is to provide new and improved methods of and apparatus for contin- Vuously rapidly producing molded pulp egg cartons having a reinforced hinge portion.

Other objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a side elevation View, partially in section, of pulp molding apparatus embodying the invention;

Fig. 2 is a vertical sectional view takenalong line 2-2 of Fig. l;

Fig. 3 is an enlarged fragmentary sectional view taken along line 3 3 of Fig. l; and

Fig. 4 is a view similar to Fig. l but of a modified form of theV invention.

The molding apparatus illustrated includes aV plurality of foraminous molds mounted on the periphery of a mold carrier or drum, 12, which is partially submerged in and rotatable through a slurry of pulp stock 14 contained in an open vat 16. The drum 12 may be polygonal as shown in Fig. 4 or cylindrical in conguration as shown in Fig. 1, and it may carry twelve molds 10 equally spaced on its periphery having twelve substantially flat faces as shown in Fig. 4. Hubs 18 are provided at opposite ends of the drum 12, and it is mounted rotatably on an axial hollow shaft 20 extendingV through the hubs 18. Driving means (not shown) located outside the vat 16 is provided for rotating the drum 12 to advance the molds 10 successively through the pulp stock slurry 14.

The molds 10 are connected individually with the hollow shaft 20 by means of channels 22 extending radially through the drum 12. In the usual manner, suction means (not shown) communicating with the hollow shaft 20 causes suction to be applied internally to the molds 10 while they are submerged in the pulp stock slurry 14, thereby resulting in the deposition of a layer of wet pulp fibers on the molds 10. The initially molded article formed by this layer of wet pulp fibers is known as a preform. In order to extract some of the excess moisture from the wet pulp preforms, the suction applied to the molds 10 is continued while they emerge from and advance upwardly above the pulp stock slurry 14 during the continued rotation of the drum 12. After the successive molds 10 have risen to a predetermined extent above the upper level of the pulp stock slurry 14, the preforms are successively removed from the molds and transferred to suitable drying apparatus (not shown) of well known construction.

In order to illustrate the principles of the invention,

produce a molded pulp egg carton of the type having a cover portion connected by an integral hinge portion to a bottom portion. Merely as a matter of convenience, the drum 12 is provided with two of the molds 10 mounted in a row at each of twelve equally spaced points on its periphery. Of course, the number of molds mounted on the drum may be Varied as desired depending upon the size of the drum, and the number of molds in each row thereof may be two as shown, or only one, or many more than two. Each of the molds 10 includes a carton cover forming section 24 and a carton bottom forming section 25 joined by an intermediate hinge forming section 26.

In accordance with the invention, reinforcement of the hinge portion of the egg carton is achieved by depositing a different grade of pulp stock at the hingeforming section 26 of each mold 10 from that deposited on the rest of the mold. A slurry of long fiber pulp stock may be supplied for deposition in the hinge area, while ground wood pulp stock may be employed in the slurry 14 to form the remainder of each egg carton. The slurry of ground wood pulp stock may be supplied through a pipe '#277 while the slurry of long fiber pulp stock may be supplied through a pipe 28 extending into thevat 16 from an elevated reservoir 30. A horizontal portion 31 of the pipe 28 is submerged in the ground wood pulp stock slurry 14, and its exit end is directed toward that portion of the periphery of the drum 12 on which the hinge forrning portions 26 of the molds 10 are located, so that such portions 26 are moved successively therepast during rotation of the drum 12. An elongated U-shaped trough 32, which is curved lengthwise to conform to an arc of a circle centered on the shaft 2t) and is spaced closely to the drum 12 along a portion of its periphery, may be secured to the exit end of the pipe 28. The open side of the U-shaped trough 32 is directed toward and is aligned with the hinge forming sections 26 of the molds 10 mounted on the drum 12. It ispreferred toemploy the trough 32 in producing molded p ulpcgg cartons, but in molding certain other locally reinforced pulp articles the trough 32 may be omitted. Y j

In employing this apparatus to produce locally reinforced molded pulp egg cartons, the slurry 14 of ground Wood pulp stock may be replenished through the pipe 27 to maintain this slurry at approximately the same level and concentration during the molding operation therein. At the same time, a sufficient head of the long fiber pulp stock slurry must be maintained in the reservoir 30 to supply this slurry at a uniform rate to the pipe 28, from which this slurry is projected onto the hinge forming sections of the molds 10. Inevitably some slight intermingling of the two different pulp slurries occurs in the vicinity of the exit end of the pipe 28 and along the trough 32, and this results in the deposition of a mixture of the two different grades of pulp stock at the hinge `forming sections 26. Due to the hydraulic pressure of the slurries and the suction applied internally to each mold at its hinge forming section 26 as well as at its ,cover forming section 24 and its bottom forming section 25, the deposition 4of the long fiber pulp stock is sob- Stantially confined to the hinge forming section 26, and the layer `of pulp fibers deposited here contain a high percentage of long liber pulp stock. Furthermore, the long `fiber pulp stock penetrates through to the forming face of the hinge forming section 26 of the mold 10, at which point it is most needed in the completed egg carton. Substantially only the ground wood pulp stock is deposited at the carton coverforming section 24 and the carton bottom forming section 25 of each mold 10. By this method, the deposition of the long fiber pulp stock is effectively restricted in area to provide localized reinforcement in the egg carton produced.

Ordinarily, the drum 12 is rotated through the slurry y1-.4 in a counter-clockwise direction, as viewed in Fig. 1. When long ber pulp stock is supplied to Vthe trough 32 while ground wood pulp stock is supplied to the remainder of the vat 16, this counterclockwise motion results in the deposition on the hinge forming section 26 of an initial layer of long fiber pulp stock, followed by an intermediate `layer of mixed stock, and finally a layer of ground wood stock. In some instances it might be desirable to reverse the order in which these layers are deposited, and thiscan be accomplished merely by rotating the drum 12 in a clockwise direction during the deposition operation.

The horizontal portion 31 of the pipe 28 is located submerged just below the surface of the slurry 14 near what is the entrance end of the vat 16 with respect to the movement of the molds 10 during the normally counter-clockwise rotation of the drum 12. By installing a second pipe and trough (as `shown in Fig. 4) at the exit end of vat 16 andsupplying long fiber pulp stock thereto, it is possible to deposit long ber pulp stock in both the initial and final layers on the hinge forming section 26, and to deposit the ground wood pulp stock intermediately.

The invention has been illustrated and described with particular reference to the production of locally reinforced molded pulp egg cartons, but it should be understood that the principles of the invention may be applied advantageously in the production of other types of locally modified or reinforced molded articles including, but not limited to molded pulp articles. Although specific reference has been made to molded pulp articles, the use of other bers is also contemplated, including any suitable animal, vegetable or mineral fibers. For example, glass fiber articles may be readily made by similar methods and apparatus. Furthermore, certain well known plastic compositions or other additives may be incorporated therein.

It will be obvious `to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and -described in the specification, but only as indicated in the appended claims.

`What is claimed is:

1. A method of producing molded pulp egg cartons having a reinforced integral hinge portion, comprising `advancing `tltrough a slurry of one grade of pulp `stock a series of foraminous suction molds designed to form such a carton and having a hinge forming section, and projecting a slurry of a reinforcing grade of pulp stock onto the hinge forming sections only of the molds while they are submerged in and are being advanced through the frstmentioned slurry.

2. A method of producing molded pulp egg cartons having a reinforced integral hinge portion, comprising advancing through a slurry of one grade of pulp stock a series of foraminous suction molds designed to form such a carton and having a hinge forming section, projecting a slurry of a reinforcing grade of pulp stock onto the hinge forming sections only of the molds while they are submerged in and are entering the first-mentioned slurry, and projecting another reinforcing grade of pulp stock onto said hinge forming sections only while they are submerged in and are emerging from said first-mentioned slurry.

3. A pulp molding machine for producing egg cartons having an integral hinge portion joining a carton bottom portion to a carton cover portion, said machine comprising a mold carrier mounted rotatably partially submerged in a vat containing a slurry of pulp stock, a plurality of foraminous molds mounted on the periphery of the carrier, `each mold having a hinge forming section intermediate a cover forming section and a bottom forming section, said molds being subjected to suction internally to cause the pulp stock to be deposited thereon as the molds are advanced successively through the slurry during rotation of the carrier, a pipe for supplying the vat with a slurry of one grade `of pulp stock, and another supply pipe located in the vat and directed toward the periphery of the mold carrier in alignment with the hinge forming sections of the molds thereon for projecting a slurry of a different grade of pulp stock thereon restricted to the hinge forming sections of the molds being advanced therepast while the first-mentioned pulp stock is deposited on the other sections of the molds.

4. A pulp molding machine for producing egg cartons having an integral hinge portion joining a carton bottom portion to a carton cover portion, said machine compris ing a mold carrier mounted rotatably partially submerged in a vat containing a slurry of pulp stock, a plurality of foraminous molds mounted on the periphery of the carrier, each mold having a hinge forming section intermediate a cover forming section and a bottom forming section, said molds being subjected to suction internally to cause the pulp stock to be deposited thereon `as the molds are advanced successively through the slurry during rotation of the carrier, an elongated trough curved lengthwise to conform to the shape of the mold carrier and mounted submerged in the slurry spaced closely to the carrier along a portion of its periphery aligned with the hinge forming sections of the molds thereon, a pipe for supplying a slurry of one grade of pulp stock to the vat, and a second pipe for supplying the trough with a slurry of a different grade of pulp stock, whereby the deposition of said different pulp stock from the trough is restricted to the hinge forming sections of the molds while the pulp stock supplied to the vat is deposited on the other sections of the molds.

5. A pulp molding machine `for producing egg cartons having an integral hinge portion joining a carton bottom portion to a carton cover portion, said machine comprising a generally cylindrical mold carrier mounted rotatably partially submerged in a vat containing a slurry of pulp stock, a plurality of foraminous molds mounted on the periphery of the carrier, each mold having a hinge forming section intermediate a cover forming section and a bottom forming section, said molds being subjected to suction internally to cause the pulp stock to be deposited thereon as the molds are advanced successively through the slurry during rotation of the carrier, a pair of elongated U-shaped troughs curved lengthwise to conform to the curvature of the carrier and mounted submerged in the slurry spaced closely to the carrier along a portion of its periphery in alignment with the hinge forming sections of the molds, one of said troughs being mounted on one side of the vat where the molds enter the slurry and the other trough being mounted on the opposite side of the vat where the molds emerge from said slurry, a pipe for supplying said slurry to the vat, and a pair of supply pipes communicating with the pair of troughs for supplying them with a slurry of a dierent grade of pulp stock, whereby the deposition of said different grade of pulp stock is restricted to the hinge forming sections of the molds while the slurry supplied to the vat is deposited on the other sections of the molds.

References Cited in the file of this patent UNTED STATES PATENTS 

1. A METHOD OF PRODUCING MOLDED PULP EGG CARTONS HAVING A REINFORCED INTEGRAL HINGE PORTION, COMPRISING ADVANCING THROUGH A SLURRY OF ONE GRADE OF PULP STOCK A SERIES OF FORAMINOUS SUCTION MOLDS DESIGNED TO FORM SUCH A CARTON AND HAVING A HINGE FORMING SECTION, AND PROJECTING A SLURRY OF A REINFORCING GRADE OF PULP STOCK ONTO THE HINGE FORMING SECTION ONLY OF THE MOLDS WHILE THEY ARE SUBMERGED IN AND ARE BEING ADVANCED THROUGH THE FIRST-MENTIONED SLURRY 